An international team of astronomers, in which Spanish researchers have also participated, has discovered a surprising abundance of massive stars in a neighboring galaxy, specifically in the 30 Doradus region of the great galaxy of the Magellanic Cloud.
The finding has important consequences for our understanding of how stars transformed the pristine universe in which we live today. “We were surprised when we realized that 30 Doradus has formed many more massive stars than expected,” says Fabian Schneider, of the Physics Department of the University of Oxford (United Kingdom) and leader of the study published in the journal Science.
Thanks to the Very Large Telescope (VLT) of the European Southern Observatory (ESO) and within the VLT-FLAMES Tarantula Survey, astronomers observed almost 1,000 massive stars in 30 Doradus, a gigantic star nursery also known as the Tarantula Nebula. The team used detailed analyzes of around 250 stars with masses between 15 and 200 times the mass of our Sun to determine the distribution of massive stars born in 30 Doradus.
Massive stars are particularly important to astronomers due to the enormous influence they cause in their environment: they can explode in spectacular supernovas at the end of their lives, forming some of the most exotic objects in the universe: neutron stars and black holes.
Apart from the surprise for the large number of massive stars discovered, scientists are also stunned by the density of them (up to 200 solar masses). Above all, considering that the existence of stars of up to 200 solar masses was very controversial. This study shows that a maximum birth mass of stars of 200-300 solar masses is likely.
The stars become more rare – or exotic – the more massive they are. Until now we believed that the majority of the star mass was in stars of low mass and that less than 1% of all stars were born with masses that exceed ten times that of the Sun. It is clear that we lacked information.
The largest local star formation region
30 Doradus houses some of the most massive stars ever discovered. Studying this region, researchers determined the masses of massive stars with unique observational, theoretical and statistical tools. This large sample allowed scientists to show that massive stars are much more abundant than previously thought.
“In fact, our results suggest that most of the stellar mass is no longer at low levels,” explains Chris Evans, of the Astronomy Technology Center of the Scientific and Technological Facilities Council of the United Kingdom, and co-author of the study.
“Our results have far-reaching consequences for the understanding of our cosmos: there may be 70% more supernovae, a tripling of chemical yields and four times the ionizing radiation of massive star populations. Blacks could increase by 180%, which directly translates into an increase in binary black hole mergers that have recently been detected through their gravitational wave signals,” concludes Schneider.